Method for electrochemical metallization of a double-sided electrical circuit for a smart card and electrical circuit produced using said method

Abstract

Method for the electrochemical metallization of a double-sided electrical circuit for a chip card. Contacts and current leads are located on a front face. An antenna and connection pads are located on a rear face. This method includes an operation of electrochemically depositing at least one layer of electrically conductive material on connection pads, while supplying these connection pads with current via the current leads, contacts and metallized holes establishing electrical continuity between the front face and the rear face. This method furthermore includes, after the operation of electrochemically depositing at least one layer of electrically conductive material, an operation of electrically isolating at least one metallized hole from a connection pad. Electrical circuit obtained using this method.

The invention claimed is: 
     
       1. A method for the electrochemical metallization of a double-sided electrical circuit for a chip card with contact-based and contactless communication, the method comprising:
 providing a flexible dielectric substrate, where the flexible dielectric substrate comprises a front face and a rear face, where the front face comprises a plurality of contacts and a plurality of current leads thereon, where the plurality of current leads are electrically connected to at least two of the plurality of contacts, where the rear face comprises an antenna and a plurality of connection pads thereon, where at least two of the plurality of connection pads are dedicated to connecting a chip to the plurality of contacts, and at least one different connection pad of the plurality of connection pads is dedicated to connecting the chip to the antenna, 
 electrochemically depositing at least one layer of electrically conductive material on the plurality of the connection pads, while supplying the plurality of connection pads with current via the plurality of current leads, where the plurality of contacts and metallized holes establish electrical continuity between the front face and the rear face, 
 after the electrochemically depositing of the at least one layer of electrically conductive material, electrically isolating at least one of the metallized holes from one of the plurality of connection pads which is dedicated to connecting the chip to the antenna. 
 
     
     
       2. The method according to  claim 1 , wherein at least two of the metallized holes are used, during the electrochemically depositing at least one layer of electrically conductive material, to metallize an internal antenna connection pad of the plurality of connection pads and an external antenna connection pad of the plurality of connection pads, where at least one of the at least two metallized holes is electrically isolated from the internal and external antenna connection pads in an operation following the electrochemically depositing of the at least one layer of electrically conductive material. 
     
     
       3. The method according to  claim 1 , wherein a first one of the plurality of contacts on the front face is connected to two separate ones of the plurality of connection pads, where the first contact is used to supply power to the two connection pads during the electrochemically depositing of the at least one layer of electrically conductive material, with use of two of the metallized holes, where at least one of the two metallized holes is then subsequently electrically isolated from each of the two connection pads. 
     
     
       4. The method according to  claim 1 , further comprising electrically isolating, using a laser beam, at least one of the metallized holes from one of the plurality of connection pads which is dedicated to connecting the chip to the antenna. 
     
     
       5. The method according to  claim 4 , wherein the laser beam is moved over a surface of a conductive area connecting the at least one metallized hole to the connection pad dedicated to connecting the chip to the antenna, without leaving the surface around the at least one metallized hole in order to isolate the at least one metallized hole from a rest of the connection pad dedicated to connecting the chip to the antenna. 
     
     
       6. A double-sided electrical circuit for a chip card with contact-based and contactless communication, comprising:
 a flexible dielectric substrate, where the flexible dielectric substrate comprises a front face and a rear face, 
 a plurality of contacts and a plurality of current leads located on the front face, 
 an antenna and plurality of connection pads located on the rear face, 
 where at least two first ones of the plurality of connection pads are dedicated to connecting a chip to the plurality of contacts, and second ones of the plurality of connection pads are dedicated to connecting the chip to the antenna, 
 where at least one of the plurality of contacts is located on the front face, where the at least one contact closes off at least two metallized holes, where the at least two metalized holes extend through the flexible dielectric substrate, where a first one of the metallized holes is connected to a contact connection pad of the first connection pads which are dedicated to connecting the chip to the at least one contact, and where a second one of the metallized holes is electrically isolated from an antenna connection pad of the second connection pads which are dedicated to connecting the chip to the antenna. 
 
     
     
       7. The double-sided electrical circuit according to  claim 6 , wherein an external antenna connection pad of the plurality of connection pads is electrically connected to the antenna with two second ones of the metallized holes, where the two second metallized holes are closed off by a conductor track located on the front face. 
     
     
       8. The double-sided electrical circuit according to  claim 6 , wherein an external antenna connection pad of the plurality of connection pads is electrically connected to the antenna with one of the plurality of contacts. 
     
     
       9. The double-sided electrical circuit according to  claim 6 , wherein the antenna forms at least one loop around a central area corresponding to an area for fastening of the chip, where the plurality of connection pads comprise contact connection pads and antenna connection pads, and wherein all of the contact connection pads and antenna connection pads are located around the central area within a loop of the antenna. 
     
     
       10. The double-sided electrical circuit according to  claim 6 , comprising a further metallized hole which extends through the flexible dielectric substrate, where the further metallised hole is electrically isolated from all of the plurality of connection pads, where the further metallized hole is surrounded by an isolating region resulting from abrasion produced by a laser beam.